Its warming up this week and I'm getting ready to really get moving on my coach. So right now i'm just looking over all my plans for the 40th time. The one thing i never tackled is my water hookup inlet. I've been meaning to ask, but keep forgetting. Anyways, what places are there where i can fill up my clean water tanks that arent campgrounds (since i will never be at one). I remember one time i saw an rv water filling station at a rest stop, but i havent seen them too often, so are they always at every rest stop, or what exactly.

Not all rest areas have dump stations and always check with the attendant at any rest area that does to be sure that is it potable water! Many times there is supposed to be a sign saying if it is or not, but with vandals you never no fer sure! Also almost all Flying J's have it on their RV island. Many LOVES now have them, and some Pilot's too! BK

Only water hose I recall seeing at reat areas were near a dump station and for flushing out your dump hoses. They were clearly marked "NOT POTABLE WATER". Usually very short and no hose fitting on the end to prevent them from being used for anything except what they were intended for. Jack

I haven't tried it myself, but I've heard people mention various instances of paying a convenience store or restaurant to let them connect to an outside tap for a fill. You would have to have a long enough fresh water hose to reach though.

I would second BK's advice about Flying J's. And I suspect many of the smaller truck stops would fall in the category I mentioned above, negotiate your own deal with them.

As for dump stations (what goes in, must come out), here is a link to a site that lists known dump stations by state:

Remember when the fresh water is empty the waste tanks will be full and every state does not have dump stations. So along with truck stops most campgrounds will let you dump and take on fresh water for a small fee even if you are not staying there.($5.00 to $10.00) With our 100 gallon tanks we can go 7-10 days before dumping so that has not been a problem. Check online for campgrounds and truck stops along your route.

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Terry"Far away there in the sunshine are my highest aspirations. I may not reach them, but I can look up and see their beauty, Believe in them, and try to follow them." ~Louisa May Alcott~www.awayweare.blogspot.com/

Remember when the fresh water is empty the waste tanks will be full ...

Not necessarily. Fresh water is waaaay easier to come by than a dump station. So my advice to self-converters has consistently been to install larger waste tanks than fresh tanks. We have 200 gallons of waste tankage, and only 135 gallons of fresh water, although we also have a separate 40 gallon tank for drinking water.

Aside from the issue of differently-sized tanks, however, we also do not travel with full fresh (or drinking) tanks unless we are going into the wilderness. Water is heavy, 8.35 pounds per gallon. A full tank for us weighs in at over half a ton -- 1,125 pounds. I'm not going to waste diesel hauling that amount of weight up every hill when I know I can get water almost anywhere in the country.

We typically carry enough fresh water for two days, which, for us, is 20 gallons.

Dump stations, OTOH, are fewer and further between, especially if you're looking for free ones as we are. Even when we come across them more frequently, though, we seldom dump our tanks if they are less than half full. More often, they are nearly full when we dump.

So, bottom line, we go about two weeks between dump stations, and never less than one week, whereas we are putting water in every two or three days when we are moving. Again, the exception is going into the boonies; we'll dump the waste and top up both the fresh and drinking water supplies before heading off into the national forests or the BLM desert, then spend two weeks there.

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... and every state does not have dump stations.

Well, actually, we have found free dump stations in every state we've been in (42 so far). Many states have closed their state-operated dumps at, e.g., freeway rest areas. But, by using the web site cited above, plus other web resources as well as printed guides, we have always been able to locate a free dump station when we needed it. In four and a half years of full-timing, we have only paid explicitly to dump twice. Once was when we were in an urban area for longer than two weeks, and the $5 dump fee was less than what we'd spend in diesel to go elsewhere for a free dump, and the other time was when we asked the bus garage that was doing some repair work if we could use their dump -- when they said "yes," they neglected to tell us they would tack a $25 fee onto our bill (lesson learned).

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So along with truck stops most campgrounds will let you dump and take on fresh water for a small fee even if you are not staying there.($5.00 to $10.00) With our 100 gallon tanks we can go 7-10 days before dumping so that has not been a problem. Check online for campgrounds and truck stops along your route.

Flying-J, which has dump stations at most of its truck stops, has an on-line directory. All major truck stop chains have on-line locators, and almost every truck stop will have water freely available at the fueling islands. Be forewarned, though, that some stations shut the water off when the temperature drops below freezing.

Many Interstate rest areas have water spigots, even if there is no dump station. We've also had no trouble getting water on request from Forest Service offices, ranger stations, gas stations, chambers of commerce visitor centers, and countless other businesses. We also carry a four-way valve key to activate hose bibs on the outside of commercial buildings, which is often how we have to get water when we are on Red Cross assignments.

But for some of us that live in our Bus also we just fill our fresh water and empty our waste water,when we run low on fresh or start to fill up on waste we stop. But you do it your way water and dump are available.

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Terry"Far away there in the sunshine are my highest aspirations. I may not reach them, but I can look up and see their beauty, Believe in them, and try to follow them." ~Louisa May Alcott~www.awayweare.blogspot.com/

I've considered your theory of carrying minimal water because of weight but long ago decided that having adequate water for that unplanned emergency far outweighed the extra fuel burned carrying it around.

That very thing happened to us recently when a surprise ice storm sent us into an unplanned stay at a WM parking lot.

I've considered your theory of carrying minimal water because of weight but long ago decided that having adequate water for that unplanned emergency far outweighed the extra fuel burned carrying it around.

That very thing happened to us recently when a surprise ice storm sent us into an unplanned stay at a WM parking lot.

That's why we always carry at least two days' worth of fresh. We usually have several days of drinking water, too, so we can weather pretty much any emergency or unplanned stop. It's two weeks' worth that I can't see carrying around unless I need it.

For the same reason, when fuel prices are consistent (such as when traveling in Mexico, for instance, or staying within one state such as Texas), we don't put more fuel in than we have to. The difference in weight for us between half a tank and a full tank is also over half a ton -- 1,100 pounds. Traveling with half water and half fuel saves a full ton; keeping the waste tank empty saves another ton (on average).

Of course, fuel prices vary widely by state, and we end up arbitraging the fuel price, topping up when it's low, and running light when it's high.

Sean, have you actually been able to gauge any fuel savings based on carry less weight? It seems that aerodynamic drag would have more affect on mileage when driving on the highway at a fairly constant speed.

I haven't done enough travel without being loaded to the hilt to be able to determine if MPG is affected by weight.

Sean, have you actually been able to gauge any fuel savings based on carry less weight? It seems that aerodynamic drag would have more affect on mileage when driving on the highway at a fairly constant speed.

I'd love to say "yes" and give you hard numbers. However, since my DDEC, for whatever reason, is not reporting distance traveled (no one at DDC has been able to figure out why), my overall MPG display does not work. And there's too much "play" in my large-surface-area 350 gallon tank to get accurate results doing it the old fashioned way.

That said, it does not take much math to set a lower bound on the savings.

If vehicles moved through a vacuum on flat frictionless surfaces, then it would take no energy at all to move them at constant speed. However, in the real world, there are five factors that conspire to "use up" energy, almost all of which ends up in the environment as heat:

Aerodynamic drag, as you've noted

Rolling resistance (friction)

Acceleration forces

Efficiency loss of the powerplant

Accessories (e.g. alternator)

Aerodynamic drag, which is a large element, is mostly unaffected by weight. And the inefficiencies of the powerplant, which show up as unburned fuel going out the exhaust, as well as heat shed through both the cooling and exhaust systems, can be thought of, for our purposes, as a constant percentage of the total expenditure. Accessory power is mostly constant over time and can simply be subtracted from the equation; for most of us, a small percentage. That leaves rolling resistance and acceleration forces.

Rolling resistance increases directly with weight. The energy required to overcome rolling resistance thus also directly increases with weight. So if you add, say, 5% to the weight of your bus, it will require 5% more energy to overcome the rolling resistance, and, assuming losses in the powerplant are a constant percentage, 5% more fuel. This is more or less irrespective of speed.

Acceleration forces, though, are the killer here. In our "perfect" universe, with no friction and no air, it does still take energy to accelerate the mass of the vehicle to a certain speed. Energy must also be expended to decelerate the mass back down to zero, or to change direction, even at constant speed.

Here again it is a direct relationship. It takes 5% more energy, thus 5% more fuel, to accelerate your bus if you add 5% to the weight. The good news is that, because of friction, we can decelerate the bus without expending additional energy -- we simply take the kinetic energy of the bus in motion, and translate it to heat using the brakes.

It's tempting then to say that, OK, once I've accelerated to speed, and set the cruise control, now I'm done with the acceleration forces, and the weight no longer matters, as all the mass is already in motion. Surely the rolling resistance, which we already discussed, is not enough to worry about. The problem with this line of thought is that roads are neither straight, nor flat. So every time you are on an upgrade of any kind, you are "accelerating" up the grade. Once at the top of the grade, to maintain a constant speed, you will now be braking (whether that's with regular brakes, retarder, or Jakes, all of which translate deceleration into heat) on the downgrade. So, effectively, all the energy (and thus fuel) you used to climb the grade is given back to the environment as heat on the other side.

Also, every curve represents acceleration. If you do not increase throttle in a curve, the coach will slow down, because energy is expended in the form of heat at the tires when negotiating a curve. All of this energy, and thus fuel, is again directly related to weight.

So what it comes down to is this: At any given speed, what percentage of your energy loss (and thus fuel use) is related to acceleration and rolling resistance, and what percentage is related to aerodynamic drag? This is where we move away from direct relationship and into a square relationship -- aerodynamic resistance increases as the square of the speed.

It turns out that at around 25mph or so, it takes around twice as much energy to overcome rolling resistance and internal losses as it does to overcome aerodynamic drag. At about 50 or so, they are about equal. Somewhere just north of 70mph the drag losses are double the rolling losses, and at 80mph they are treble. (From research on heavy trucks.)

If you do all your driving around town, up to around 25mph, adding 10% to your weight will cost you 7% or more in fuel. If you drive at a constant 80mph on straight, level roads, adding 10% to your weight could cost you as little as 3% more fuel. And if you go up and down grades all day long, adding 10% to your weight can cost you nearly that same 10% in extra fuel.

For me, personally, I am so painfully aware of the speed-squared effects of drag that we seldom drive over 55mph. Even on 75 and 80 posted freeways, we dial the cruise in at 61 unless we are going to a disaster. So for me, even on that mythical straight, flat highway, every percent I add to the weight adds nearly half a percent to fuel consumption. But because most of our driving is on two-lane, where grade and alignment are not as controlled as on the Interstate, the effect is even greater, perhaps 3/4 or more of a percent for every percent gain in weight. That extra ton of water and fuel, BTW, represents about 4.5% of our GVW. So by having it on board, I'm using perhaps 3% more fuel than necessary. I know that's not a lot, but if someone offered you a 3% discount program on your fuel, I'd bet you'd take it in a heartbeat.

"Rolling resistance increases directly with weight. The energy required to overcome rolling resistance thus also directly increases with weight. So if you add, say, 5% to the weight of your bus, it will require 5% more energy to overcome the rolling resistance, and, assuming losses in the powerplant are a constant percentage, 5% more fuel. This is more or less irrespective of speed."At worst it would be 5% increase in that part of the fuel used to overcome rolling resistance. Rolling friction due to tyre deformation is only part of the friction problem. Engine friction, gearbox and other parts of the transmission and drivetrain must surely add significant losses

I would have thought that if you increased the pressure in the tyres in accordance with the increased mass, then the increase in rolling resistance could largely be eliminated.

At worst it would be 5% increase in that part of the fuel used to overcome rolling resistance. Rolling friction due to tyre deformation is only part of the friction problem. Engine friction, gearbox and other parts of the transmission and drivetrain must surely add significant losses

I'm not talking about tire deformation at all. My statements presume that the tires will be properly inflated for the load. I'm talking about rolling friction in the strict sense -- even if the wheels are steel, such as on a railroad car, the rolling resistance increases in direct proportion to the weight. That includes losses in the bearings, where it manifests as heat.

The other losses you mention in the engine, gearbox, drivetrain, etc. are what I referenced originally as "powerplant losses" -- generally in the 30% range.

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I would have thought that if you increased the pressure in the tyres in accordance with the increased mass, then the increase in rolling resistance could largely be eliminated.

No, but the contrary is certainly true: if you fail to increase tire pressure in accordance with the increased weight, then the losses will increase beyond a direct proportion. IOTW, if you add 10% to the weight, it will take more than 10% additional energy to overcome. The best you can do is 1-for-1.